1 files changed, 74 insertions, 1 deletions

diff --git a/builtin/ls-files.c b/builtin/ls-files.c
index f6f9e483b2..60a2913a01 100644
--- a/builtin/ls-files.c
+++ b/builtin/ls-files.c
@@ -12,6 +12,7 @@
 #include "dir.h"
 #include "builtin.h"
 #include "tree.h"
+#include "cache-tree.h"
 #include "parse-options.h"
 #include "resolve-undo.h"
 #include "string-list.h"
@@ -420,6 +421,53 @@ static int get_common_prefix_len(const char *common_prefix)
 	return common_prefix_len;
 }
 
+static int read_one_entry_opt(struct index_state *istate,
+			      const struct object_id *oid,
+			      struct strbuf *base,
+			      const char *pathname,
+			      unsigned mode, int opt)
+{
+	int len;
+	struct cache_entry *ce;
+
+	if (S_ISDIR(mode))
+		return READ_TREE_RECURSIVE;
+
+	len = strlen(pathname);
+	ce = make_empty_cache_entry(istate, base->len + len);
+
+	ce->ce_mode = create_ce_mode(mode);
+	ce->ce_flags = create_ce_flags(1);
+	ce->ce_namelen = base->len + len;
+	memcpy(ce->name, base->buf, base->len);
+	memcpy(ce->name + base->len, pathname, len+1);
+	oidcpy(&ce->oid, oid);
+	return add_index_entry(istate, ce, opt);
+}
+
+static int read_one_entry(const struct object_id *oid, struct strbuf *base,
+			  const char *pathname, unsigned mode,
+			  void *context)
+{
+	struct index_state *istate = context;
+	return read_one_entry_opt(istate, oid, base, pathname,
+				  mode,
+				  ADD_CACHE_OK_TO_ADD|ADD_CACHE_SKIP_DFCHECK);
+}
+
+/*
+ * This is used when the caller knows there is no existing entries at
+ * the stage that will conflict with the entry being added.
+ */
+static int read_one_entry_quick(const struct object_id *oid, struct strbuf *base,
+				const char *pathname, unsigned mode,
+				void *context)
+{
+	struct index_state *istate = context;
+	return read_one_entry_opt(istate, oid, base, pathname,
+				  mode, ADD_CACHE_JUST_APPEND);
+}
+
 /*
  * Read the tree specified with --with-tree option
  * (typically, HEAD) into stage #1 and then
@@ -436,6 +484,8 @@ void overlay_tree_on_index(struct index_state *istate,
 	struct pathspec pathspec;
 	struct cache_entry *last_stage0 = NULL;
 	int i;
+	read_tree_fn_t fn = NULL;
+	int err;
 
 	if (get_oid(tree_name, &oid))
 		die("tree-ish %s not found.", tree_name);
@@ -458,9 +508,32 @@ void overlay_tree_on_index(struct index_state *istate,
 			       PATHSPEC_PREFER_CWD, prefix, matchbuf);
 	} else
 		memset(&pathspec, 0, sizeof(pathspec));
-	if (read_tree(the_repository, tree, 1, &pathspec, istate))
+
+	/*
+	 * See if we have cache entry at the stage.  If so,
+	 * do it the original slow way, otherwise, append and then
+	 * sort at the end.
+	 */
+	for (i = 0; !fn && i < istate->cache_nr; i++) {
+		const struct cache_entry *ce = istate->cache[i];
+		if (ce_stage(ce) == 1)
+			fn = read_one_entry;
+	}
+
+	if (!fn)
+		fn = read_one_entry_quick;
+	err = read_tree(the_repository, tree, &pathspec, fn, istate);
+	if (err)
 		die("unable to read tree entries %s", tree_name);
 
+	/*
+	 * Sort the cache entry -- we need to nuke the cache tree, though.
+	 */
+	if (fn == read_one_entry_quick) {
+		cache_tree_free(&istate->cache_tree);
+		QSORT(istate->cache, istate->cache_nr, cmp_cache_name_compare);
+	}
+
 	for (i = 0; i < istate->cache_nr; i++) {
 		struct cache_entry *ce = istate->cache[i];
 		switch (ce_stage(ce)) {